1. Field
The present invention relates to a manufacturing method of an antireflection article, an antireflection article, a cover glass, and an image display device.
2. Related Art
In an image display device such as a cathode ray tube display device (CRT), a plasma display panel (PDP), an electroluminescence display (ELD), a vacuum fluorescent display (VFD), a field emission display (FED), and a liquid crystal display (LCD), an antireflection function is generally imparted in order to prevent a reduction in contrast or glare of an image due to the reflection of external light on a display surface of the device. Further, the antireflection function may be imparted in any case other than the image display device.
As a method of imparting the antireflection function, there is a method of using an antireflection article including an antireflection layer provided on a substrate. An antireflection layer has been known, which includes, on the surface of a substrate, an antireflection layer having a fine unevenness shape in which a period is equal to or shorter than the wavelength of the visible light, that is, an antireflection layer having a so-called moth eye structure. By the moth eye structure, a refractive index gradient layer whose a refractive index is continuously varied from the air towards a bulk material inside the substrate is artificially produced, so that reflection of light may be prevented.
As an antireflection layer having the moth eye structure, Japanese Patent Laid-Open Publication No. 2009-139796 (hereinafter JP-A-2009-139796) describes an antireflection layer having an unevenness structure manufactured by applying an application liquid containing a transparent resin monomer and fine particles on a transparent substrate, curing the application liquid to form a transparent resin dispersed with the fine particles, and then, etching the transparent resin.
Further, although there is no mention about the moth eye structure, Japanese Patent Laid-Open Publication No. H5-13021 describes a method of manufacturing an anti-reflector in which an application liquid including tetraethoxysilane and ultrafine particles is applied on a glass substrate and calcined so that the ultrafine particles are fixed by a thin film of SiO2 produced by decomposition of the tetraethoxysilane.
Although there is no mention about the moth-eye structure, Japanese Patent Laid-Open Publication No. 2002-234754 describes a glass article on which a functional thin film is covered by a sol-gel method.
[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-139796
[Patent Document 2] Japanese Patent Laid-Open Publication No. H5-13021
[Patent Document 3] Japanese Patent Laid-Open Publication No. 2002-234754
However, in the antireflection layer described in JP-A-2009-139796, it has been found that, when high pressure is applied to a moth eye structure formed by particles in the thickness direction, the particles are crushed, thereby causing a problem in that the antireflection function is lost. Further, as the spread of smartphones or tablet PCs, the opportunity to use smartphones or tablet PCs outdoors is increased, so that it is also required to further reduce the reflectance and the haze in order to obtain the visibility under very bright environments.
As described above, an object of the present invention is to provide an antireflection article including an antireflection layer having a moth eye structure on a substrate, in which the hardness is high, the durability against pressure in the thickness direction of the moth eye structure is high, and the reflectance and the haze are low. In addition, another object of the present invention is to provide a manufacturing method by which the antireflection article is conveniently manufactured. Furthermore, still another object of the present invention is to provide the antireflection article, or a cover glass and an image display device, which include the antireflection article manufactured by the manufacturing method.
The present inventors have intensively studied and found that the above-described problem can be solved by using an antireflection article including an antireflection layer on a transparent substrate with a certain compressive stress, in which the antireflection layer contains a certain binder, as well as a first particle group composed of metal oxide particles which form a convex portion having the unevenness shape, and a second particle group composed of metal oxide particles between the first particle group and the substrate.